1. Field of the Invention
This invention relates generally to earphone-type devices, and more particularly to a personal hearing system which affords a user complete control over what they hear.
2. Description of the Related Art
Various kinds of headphones and earphones are currently used as personal hearing devices. Each device has its applications and shortcomings.
Earphones are generally of two types: earphones which seal the ear canal, and “ear buds”. An ear-sealing earphone is arranged to seal the ear canal when used, and thus must be removed for normal hearing of outside sound. Sealing the ear canal serves to effectively block outside sound and provide good audio fidelity, but is less comfortable and subjects the user to the “occlusion effect” because the ear canal is blocked. If a user's ear canal is sealed, vibrations caused by his voice and other body-conducted sounds are greatly accentuated; the effect is described as sounding like being inside a barrel.
Similarly, headphones which form a seal around the ear can deliver good audio fidelity, block outside sound and can be reasonably comfortable to wear, but are bulky and not suitable for everyday portable use.
The other earphone type—“ear buds”—fit loosely in the concha of the ear. They are comfortable, light and portable, but provide relatively poor audio fidelity. They do not block outside sound. This is both a strength and weakness of the design. By not sealing the entrance to the ear, the user does not experience the annoying occlusion effect caused by having a sealed ear canal. But by not sealing the ear canal, outside sound freely leaks into the user's ear, while reproduced sound leaks out, thereby compromising privacy. Furthermore, the low frequency response of an ear bud-type earphone tends to be poor.
Various methods have been tried to ameliorate the undesirable distortion caused by the occlusion effect. For example, some ear-sealing hearing aids provide small vents between the inside and outside of the ear canal. These vents help, but do not eliminate the effect. Deeply fitted hearing aids exhibit less of the effect, but are uncomfortable and difficult to insert.